Low-voltage rectifier protection



May 24, 1949. JENSEN 2,471,216

LOW-VOLTAGE RECTIFTER PROTECTION Filed Oct. 18, 1945 INVEN TOR.

OTTO denser) ATTORNEYS Patented May 24, 1949 UNITED STATES PATENT OFFICE LOW-VOLTAGE RECTIFIER PROTECTION Otto Jensen, Maivern, Pa, assignor to I-T-E Circuit Breaker Company, Philadelphia, Pa., a corporation of Pennsylvania Application October 18, 1945, Serial No. 623,109

3 Claims. 1

My present invention relates to circuit interrupters and more particularly to a method for the utilization of a. single circuit interrupter for full protection and isolation of mercury arc rectifier circuits.

In a mercury arc rectifier circuit used for in stance for furnishing direct current to a number of electrolytic cells in the manufacture of metals, such as aluminum or magnesium, it is desirable on the occurrence of fault conditions that the anode and cathode sides of the mercury arc rec tifier be immediately and simultaneously opened.

In such mercury arc rectifier circuits, the anode side is fed from a three-phase A. C. line con nected to the delta connected primary of a transformer. The mercury arc rectifier often is a six-phase unit fed from a six-phase secondary of the transformer.

I have found that full protection of the entire circuit may be obtained by the use of a fourpole circuit breaker, three of the poles of which are connected in the three-phase alternating current feeder and the fourth pole of which is connected on the cathode side of the mercury arc rectifier.

These four poles of the single circuit breaker are operated to open and closed positions simultaneously. Each of the four poles has its individual series connected overcurrent trip device connected in series in the particular conductor in which the circuit breaker pole is connected. Thus any of the series trip coils may be indi vidually adjusted to respond to a predetermined condition in the conductor in which it is connected and operation of the trip coil in response to that condition will trip the entire circuit breaker, opening all four poles simultaneously.

This arrangement of a four pole breaker is particularly applicable where the A. C. input voltage and the D. C. output voltage are approximately the same. For instance where the A. C. voltage is 440 volts and the D. C. voltage is 275 volts. In this case the requirements of the circuit breaker poles for A. C. are similar to the pole for D. C. and can be made alike as to size and spacing.

By thus arranging the poles of the circuit breaker so that three of the poles are in the three-phase alternating current line before the transformer and so that the fourth pole is in the cathode lead of-the mercury arc rectifier, full protection of the entire circuit is obtained.

Thus the trip coils connected in the A. C. line Will respond to short circuit, in the transformer, backfires, as well as toshort circuits on the cathode side of the rectifier. The pole connected on the cathode side of the rectifier Will also respond to short circuits on that side of the rectifier but may additionally be provided with a suitable time delay device permitting temporary overloads of limited magnitude to occur, but nevertheless protecting the rectifier against overload. The type of circuit breaker preferabl used for this purpose is the type shown in Patent Nos. 2,311,690 and 2,311,710.

The circuit breaker shown in these patents is a three-pole circuit breaker but it is pointed out therein that the same device may be built as a four pole circuit breaker and the device shown in those patents built as a four pole circuit breaker will perform the functions required by my invention.

It will be obvious that where the A. C. feeder is any other than a three phase circuit, an appropriate number of poles may be used in accordance with the number of conductors in the feeder, the circuit breaker being provided with the one extra pole for the cathode side of the rectifier.

Accordingly a primary object of my invention is the provision of simplified and novel circuit interrupting means connected in a novel manner to fully protect a mercury arc rectifier circuit.

Another object of my invention is the provision of a single multi-pole circuit breaker for protection of a mercury arc rectifier circuit wherein each of the feeders on the A. C. side of the transformer feeding the rectifier is protected by three poles of the circuit breaker and wherein the cathode on the positive side of the rectifier is also protected by one of the poles of the same circuit breaker.

The foregoing and many other objects of my invention will become apparent in the following description and drawing in which:

The figure shows a schematic circuit diagram illustrating the manner in which a single four pole circuit breaker may be utilized and con nected in accordance with my invention to protect a complete mercury arc rectifier circuit.

The anodes ID of the mercury arc rectifier H which has the mercury pool I 2 are each connected to the conductors l3 which in turn are connected to a six phase secondary l4 of the transformer IS. The three phase delta connected primary I6 on transformer i5 is fed from the three phase alternating current line comprising the conductors l1, l8, 19. The cathode side of the mercury arc rectifier H is connected to the conductor 20. The D. C. apparatus which is operated through the rectifier circuit is connected across the cathode conductor 20 and the negative or ground conductor 2!, which latter conductor is connected to the mid-point of the six-phase secondary [4 of transformer 15.

A single circuit interrupter 25 is provided with poles 26,.-21 28-;: 29 The; contacts at pole'-26;. are in series..ir1-...conductoral the; contacts ;of..:p.ole 21 are in series in conductor 18; the contacts of pole 28 are in series in conductor 19; and the;

1 known in the art such as under-voltage, reverse contacts of pole 29 are in series inconductorjll.

As previously pointed out, the individual poles 26, 21, 28, 29 are part of a singlegcilccuit breaker and are operated simultaneously;byr-thegsolenoid coil 24.

The circuit breaker may havethe iorm. shown. in Patents Nos. 2,311,690 and 2;31'1','710 but is a four pole circuit breaker in my invention. Each of the poles 26 to 29 iSflJI'OVidGd with an overcurrent... trip 5,6011 .30, 31,532,, 33,; respectively, so that .the cir.,cuit,-br eaken will trip in response, to the. condition "of reach. of, the lines 1 ll. :to l 9 and thencathode. eonductorim;

Operation, duek ,to circuit conditions, oi any of the. trip. coils ,30'to.'33..-wil1. IQtatB'thE-JtIiPPBI barv .36,a.nd, release the-latch 3 1. v The, spring. 38 functionsto open 'all four poles simultaneously. The, breaker 25is reclosedtby-the energization of the solenoid 24.

The trip coils 30. to,.,32,.arecalibrated to trip instantaneously. atebetweenaa and 6 times the normal.-A. C. input andas above pointedout. on operation. of.,any. of these, three trip coils. the entirejfpur pole circuit. breakerwill; open.

. .Thus. it beeseen thattinstantaneous. tripping will follow on any fault conditionqthat may occur, ontheload sid he :A, 04 circuit breaker poles .26. 2'l,..and.,28.,v These;- faultsmay occurein the transformenwindingsor leads,.at the rectifier terminalssonbeyondgthe rectifier.v in the D. G. circult... Abackfirelot therectifier-which is a flashover inside; thearectifier, from one otthe anodes.

H] to an adjacent anode is a short circuit on one phase. of the.transformenand-will; drawyfault current in atleast one-yofathe poles 726, 21 or;;28 and result. .in instantaneous; trippin *oithe breaker.

Any condition which causes the tripping of the, poles 276,. 2] or .:28,a1so;.opens pole;2.9. ;and. gives complete .isolation; of the rectifier: and; transformer. The high settingiof -the t;rip coils .38

M3 is to prev trt i niner n'ov rloadsuthat occur on momentary conditions; such, ,;as :the starting pi a ,motor.

.Overloadprotectionis proyidedtby the colt-33 in,,the po1e-29.

Accordingly, these trip coils 30 to;.32 protec.t the entire. circuit against short circuit in. the

transformer, backfiresintherectifien. and short. circuits on thQ CathQdeJOIED. C.s ide ..-of the.

rectifien:

The tripcoil 33wot-theD. Q. pole; 29 connected in the cathode conductor, should be supplied withan! a propriate: time delay-device. 34' :for...

for, aperiomofr-time less than the-time delay of he-. v r qadd vice-t e; trip ,c0i1;.33 will not operate. The time-delaydevice 534 is, however; so

constructedgas iszwell known: in the art; that on: lthmcontinuatiom Of'QSlilChfill lover-load beyond .current,.r.ate of rise .current trip or many others.

'The'po1es'26, 27 and 28 may also be equipped withaany, of ,-the protective features commonly r 1us.ed.f0,rA.-.C. circuits such as under-voltage, rc-

= verse:power and many others. Thus, if two rectifiers-are operatingin parallel and there is the diately be-isolated onboth; sides of" ir u r ak r 25.;b0thir mthalinerand the:

possibility of one of them feeding back to the otherdue; for instance, to loss of A. C. voltage on it, then the pole 29 may be equipped with a reverse current trip .device, 5 to give; ,thedesireld protection.

The. use. of additional tripping. devices; ital-dew pendent 0n. the. type 015 lprotection required. for: the particular circuits and method ot operation. By. the means herein; 4 described-there ore, the

feed-side of :thetransformer; ;Wi1 l.--proyide .a positiveprotection for;.allof the.- elementstof the rec-.

tifier set.

The ntire rectifier .unit-:willbevprotected with respect to v r u n s.lnoryshort .circu tss -ithetransformer, therectifier, and the. D,.;;Q. loadas:

On the occurrence of any Of fihESQCQlldi'bi-QHSJ the entire; mercury 3 are, rectifier set il load.

A2 swit h .35; s. som times. used to.:iso1a e.;t re tifier from" the negativelead for. mamtenanc This is particularly true if more than ,onelscurce,

i feedinsxthen. (3.. 516.8101 ifi-the negative dead-is ungrounded.- I claim 1. In arectifier: circuit .comprisinga,plurality of alternating current conductors connected to theprimary of atransformer, a rectifier having an, anode connectedtcthe secondary oftlreatrans-i.

former. and a;,cathode connectedtc a;direct..current .conductor .a protective-device comprising. a

,multipole' circuit breaker; the;"-poles: ojtthe ecircuit breaker being: simultaneously operableato open and closed position; :one of the. pol-6S1 oi -the circuit breaker being: connectedlin the: direct: current conductor;-. andrbeing calibratediortime -de vlayin response to.=over1oads; and-the-other-poles of the circuit breaker being :connect'ed in-- the al 5 ternating 7 current conductors, (each :poleof :thfi circuit breakerhaving atripping -deviceenergized by the conductonin which the pole is connected;- :teach of th tripping-devices energized by the alternating current conductors beingycalibrated 'for instantaneous trip at a predetermined current level.

2. In a rectifier cir-cuit comprising ai -plurality of alternating. current conductors -connec-ted to the-primaryof a'transfor'mer a rectifier having I an anode connected to the? secondary' 'ofthe transformer and a cathode; connected to a, direct current conductor; a protective device -compr is;-- ing a multipolecircuit breaker, -t-hepoles-of the the-man 1 circuit breaker being simultaneously operable to open and closed position; one of the poles of the circuit breaker being connected in the direct current conductor; and the other poles of the circuit breaker being connected in the alternating current conductors, each pole of the circuit breaker having a tripping device energized by the conductor in which the pole is connected; the tripping device in the direct current conductor being provided with time delay means for a delayed trip in response to predetermined current conditions up to a predetermined value continuing over a predetermined time interval and tripping instantaneously at current conditions above said predetermined value. a

3. In a rectifier circuit comprising a plurality of alternating current conductors connected to the primary of a transformer, a rectifier having an anode connected to the secondary of the transformer and a cathode connected to a direct current conductor; a protective device comprising a multipole circuit breaker, the poles of the circuit breaker being simultaneously operable to open and closed position; one of the poles of the circuit breaker being connected in the direct cur. rent conductor; and the other poles of the circuit breaker being connected in the alternating current conductors, each pole of the circuit breaker having a tripping device energized by the conductor in which the pole is connected; each 30 of the tripping devices energized by the alternating current being calibrated for instantaneous trip at a predetermined current level; the tripping device in the direct current conductor being provided with time delay means for a delayed trip in response to predetermined current conditions up to a predetermined value continuing over a predetermined time interval and tripping instantaneously at current conditions above said predetermined value.

OTTO JENSEN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,717,312 Brown et a1 June 11, 1929 1,748,451 Jonas Feb. 25, 1930 1,817,084 Keller June 14, 1932 1,837,995 Prince Dec. 22, 1931 1,863,162 Keller Aug. 4, 1931 1,966,810 Burnham July 17, 1934 2,056,610 Leuthold Oct. 6, 1936 2,193,083 Winograd Mar. 12, 1940 2,285,634 Issendorff et a1 June 9, 1942 FOREIGN PATENTS Number Country Date 127,291 Austria Mar. 10, 1932 

